Hydrostatically balanced jar



July 28, 19.59 'E. c. MGGARRAHAN HYDROSTATICALLY BALANCED JAR 4 sheets-sheet 2 lFiled Aug. 29. 1957 July 28, 1959 EV. C..MCGARRAHAN HYDROSTATICALLY BALANCED JAR 4 Sheets-Sheet 3 Filed Aug. 29, 1957 xx -f w.

HY DRGSTATICALLY BALANCED JAR Edward C. McGarrahan, Houston, Tex., assignor to Houston Oil Field Material Company, Inc., Houston, Tex., a `corporation of Delaware Application August 29, 1957, Serial No. 681,107

Claims. (Cl. Z55- 27) This invention relates to a device for use in well drilling operations to give a vigorous jar or impact to a string of pipe, stuck tools and the like which are lodged in a well bore, and more particularly relates to a hydrostatically balanced jar in which the cocking mechanism is subjected to substantially the same hydrostatic well pressure on each end thereby allowing the cocking mechanism to be easily cocked regardless of the fluid pressure in the well.

In drilling wells, operations are frequently hampered because tools or the string of pipe operating these tools become lodged in the bore hole and cannot be dislodged by usual means of pulling or torquing from the surface of the earth. This difficulty has partially been overcome by the development of jarring tools designed to dislodge the tools or pipe by jarring or impacting, some of which provide a jarring action while the tools or pipe are under an upward stress which permits a continuous pull on the tool or pipe during and after the blow and more effectively transmits the force of the blow to the formation from which the lodged article is desired to be freed. Certain of such jarring devices of this type make use of gas under pressure to impart the necessary jar, and one such device is shown in Patent No. 2,801,078 for a Hydraulic Jar granted July 30, 1957, on application of Weldon L. Medders and Arnal B. Foreman, Jr. While that device and other jars can be used satisfactorily during l`ordinary drilling operations, difficulty has been encountered in high pressure wells, after the cocking member has cocked the hammer element, in raising the cocking member to a position to take tension on the struck drill pipe. This is caused by the high pressures in the operating pipe acting on the cocking member and its assembly requiring that the cocking action also overcome this force in addition to applying tension on the drill pipe before the jar will become effective.

Accordingly, it is an object of the present invention to provide a hydraulic jarring device with a cocking member that is hydrostatically balanced.

A further object of the present invention is a provision of a hydraulic jar in which pressure is provided from below the cocking member to offset the hydrostatic pressure above the cocking member.

A still further object of the present invention is the provision of a balancing piston and packed olf areas which provide a hydrostatically balanced jar for use regardless of the well pressures in which the jar is used.

Other and further objects and features will be apparent from the following description lof an example of the invention given for the purpose of disclosure, taken in conjunction with the accompanying drawing, where like character references designate like parts throughout the several views, and where:

Figure 1 is a sectional side elevation of a hydrostatically balanced jar construction in accordance with the invention showing the jar at the moment the hammer element is cocked.

Figure 2 is a sectional side elevation illustrating the @2,896,915 Patented July 28, 1959 ice device of Figure `1 cocked and with an upward stress being taken on the jar,

Figure 3 is a view similar to Figure 1 and illustrates the hydrostatically balanced jar at the moment of jarring,

Figures 4A, 4B, 4C, 4D and 4E are enlarged fragmentary views of adjoining longitudinal sections, partly in section, of a hydrostatically balanced jar constructed in accordance with the invention shown at the moment of jarring.

Figure 5 is a cross sectional view taken along the line 5 5 of Figure 4B, and

Figure 6 is an enlarged fragmentary view, partly in section, of the check valve assembly of thepresent invention.

Referring now to the drawings, and particularly to Figure 1, the hydrostatically balanced hydraulic jar includes an elongated, substantially tubular, body 10, the lower end of which may be threaded or otherwise secured to the joint or substitute 12 (Figure 4E) which in turn is threaded or otherwise secured to a section of pipe or to a drilling or fishing tool, as the case may be.

The body 10 has an upper chamber 14, a middle chamber 16, and a lower chamber 18 with the lower end of the upper chamber 14 and the upper end of the middle chamber being formed by the stufling box or upper partition 20 and the lower end of the middle chamber 16 and the upper end of the lower chamber 18 being formed by the stuffing box or lower partition 22. It will be noted that these stufling boxes 20` and 22 are spaced from one another and also from the ends of the body 10. As will be apparent later, the upper chamber 14 is provided in a certain portion with gas toy effect a hammer action, and the middle chamber 16 is provided with a noncompressible liquid to initially retard the upper movement of a hammer element.

Extending downwardly into the upper end of and slidable in the upper chamber 14 is an elongate support and cocking member generally indicated by the reference numeral 24, which includes the cocking piston 26 slidable in the upper chamber 14. Referring now to Figures 4A and 4B it can be seen that preferably a brass bearing ring is provided on the cocking piston 26 to bear against the inner wall of the upper chamber 14. No packing on the cocking piston is needed as there is no iluid to be sealed by the cocking piston 26. The cocking and support member 24 also includes the hollow torque rod 30 which is secured to a top substitute 32 for suitable connection to a string of pipe 34 formani-pulation in the well bore. As illustrated this top substitute is a double box joint into which the torque rod 30 and the manipulating pipe 34 are threadably secured. In order that rotation of the manipulating pipe to which the jar is secured may be transmitted to the jar and through it to articles below, the torque rod 30 may be of any suitable shape other than round with a complementary surface in the upper portion of the body 10. As best seen in Figures 4A, 4B, and 5 the preferred form of torque rod 30 includes the keys 36 which are longitudinally slidable in the keyways 38 in the body 10. As best seen in Figure 4A the torque rod 30 slidably extends through a packing gland 40 threadedly secured in the upper end of the body 10 which packing gland 40 holds in place sealing means such as the chevron packing 42 so that that portion of the torque rod 30 which slidably extends ythrough the upper end of the body 10 is sealed against the passage of fluid into the body 10 from the exterior of the tool.

As best seen in Figure 4B that portion of the `upper chamber 14 in which the keyways 38 are located is `of reduced diameter from that portion in which the cocking piston 26 moves with said reduced portionterminating in a downwardly directed `shoulder 44. The cock- .includesthe upper piston 48 vlocated in the upper chamber 14 and the lower piston 50 in the middle chamber `16 connected to each other by :means of the hollow piston rod 52 through the upper partition or stuffing box 20. While no packing is .required on the cooking piston 26, the upper piston 48 of the hammer element ,46 is .sealed against the passage of gas .from `below it such `as by (Figures 4B and 4C) ,packing 54,held.in place on the upper Vpiston 48 between the retaining member 56 vand a brass bearing Iring 58. Another brass bearing ring 60 maybe located near the lower end of Vthe upper pis- .ton 48 (Figure 4C). Forlightness thelnpper'piston 48 between the two brassfbearingrings 58 and 60 is turned .down as at 62.V The uppenpartition or stulling box 20 has a slidable but iluid tight engagement with the piston rod 52 and is provided withpacking 64 to help .prevent leakage of fluid between rthe upper and middle chamb ers 14 and 16, respectively.

As illustrated, the cockin-g Vpiston Z6 isrnadepintegral with the lower end of the torquerod 30 except'for the lower contact ring 66 and similarly the upper piston 4S is formed integrally with the piston rod Y52. except for the retaining member Iand contact ring 56. The arrangement illustrated is satisfactory; however, the various pistons may be secured in any preferred manner.

' The middle chamber 16 is reduced in ydiameter at its lower end by the delay sleeve 66 (Figure 4D) into which the lower piston 50 snugly ts. Located on the surface of the `upper end of the lower piston 50 are a `series of circumferentially spaced guide lugs 6810 lguide the lower piston 50 when it is labove the delay sleeve 66. Thus, when Vthe lower piston-50 is positioned above the delay vsleeve 66 liquid in the middle chamber 16 is free to pass around this lower piston 50 Abetween the `guide lugs 68 .but when the lower piston 5.0 is in the position illustrated in Figure l the leakage of liquid from above the lower piston 50 will be slow thereby initially retardin-g upward movement thereof; however, when the lower .piston '50 moves out of the delay sleeve 66, the liquid readily flows around the lower piston 50 between the guide lugs 68 thereby permitting substantially unhindered upward movement of the lower piston 50.

To` facilitatedownward-movement of the piston 50 into the delay sleeve 66 there is a check valve assembly 70- in the upper portion of the lower partition 22 (Figures 4D and 6) which permits ow of liquid through the check valve assembly 70 `and a by-pass passage 72 extending from thecheck valve assembly 70-to the lmiddle chamber 1-6 above the delay sleeve 66, but which prevents the lflow of iluid upwardlyfrom below the'lower piston 5,0 when itis positioned inthe delay-sleeve 66. Thus, the hammer. element 46 may be readily cocked lwith the lower Ypiston 50 located in the confined-space at the lower end of the middle chamber orrcylinder 16. Any suitable check valve arrangement may be utilized which isso'constructed and arranged toprevent 'the llow of liquid `downwardly around the lower pistonSt) as it moves upwardly in therestricted portion of the middle chamber, 16 and to permit rapid movement around the lower piston 50 it moves downwardly.

' pbest seen in Figures 4C and 4E' a `valve such fas the inlet port 76 closed by the threaded closure. member 7 8 is-provided in the upper partition -20 so that gas ABilder Lpressure may-be. providedto the upper chamber 14;:below thelupperpistonAS. Likewise, avalve. such asfthe inlet -port 80 'closed bythe vthreaded closure. m6411- ber ;.82,(Figure 4E)f-is providedin-the'lower partition 22 so that liquid may be rovided to the middle chamber 16. It is yadvantageous to provide the inlet ports 76 and 80 at the partitionsilt) and 22 inasmuch as the metal is thicker at these points and permits of maximum strength `and compactness.

As best seen in Figures l, 2 and 3 the lower piston chamber 18 contains a balancing piston 84 connected to the supporting member 24 by the hollow connecting rod 86 extending slidably through the lower partition 22 and slidablyY through the hollow piston yrod 52 of the hammer element 46 formovement with said supporting member 24. The hollow connecting rod 86 includes a hollow support section 87 secured to its Yupper en d vvby V welding at (Figure 4A). yAt the upper end of ythe support section -87 is an enlarged external diameter portion 89 forming a downwardly facing shoulder 91 which is received by and supported by an internal shoulder 93 on the-substitute 32. Packing, such ,as the-,Q-rjng 95 prevents the passage of iluid `,between .the substitute `I32 and the enlarged diameter portion 489 and `nuts 97 threaded into the substitute 32. .hold the enlarged diameter portion 8,9 against the internal kshoulder 93. This connecting lrod S6 is hollow to provide apassage -for .fluid from the string of manipulating pipe 34 above the hydraulic jar to -below thehydranlic jar. Where connecting rod passes through the lower partition ,-22 leak- -age of fluid between the -lowerpartition 22 andthe connecting rod 86 is prevented such as by the packing 5 3 (Figure 4E) held in place by-a retainer ring 90. Fluid from the middle chamber 16 is prevented from flowing along the connecting rod 86 by ythe packing 92 in the lower piston S0 (Figure Y4D). The balancing piston 84 (Figure 4E) is threadedly securedV to the lower end or" the connecting rod S6 although it may be made integral therewith and the passage of fluid'from `above the balancing piston 84 -to below it ybetween theconnecting rod 86 and the balancing piston 84 is prevented by packing 94. The passage of fluid around the balancing piston 84 between it and the-inner wall of thelower chamber 18 is prevented by chevron-packing l9.6 on--the balancing piston 84. Between the ylowerpartition 22 and the balancing piston .84 the lower-piston chamber L8 is filled ywith .a compressible gas, such as air, while the space below the balancing piston.84 isiilled with drilling fluid passing downwardly through the hollow connect- -ing rod 86.

VThe function of this balancing piston 84 is to exert an upward force through the action lof the `hydrostatic pressure-ofthe drilling fluids below the balancing piston 84 which upward force` is applied-through the Aconnecting rod -86 to the jsupport member 2.4 fand Vis equal to the downward Acomp'o'nentof hydrostatic force of drilling fluids in and around the supportmember 24. This downward component or netdownwardly directed hydrostatic vforce on the support 'Ymember 24 exists because the lower end of the support member 24 is in the upper chamber -14 and not in contact with the drilling lluids and therefore not subject to an upward force of the hydrostatic pressure of drilling uids. Because lthe body 10 is held ixed against upward vmovement when pipe-below the jar is stuck andthe support member ,2,4 is being lifted after the cocking stroke as described later, the hydrostatic force actingupwardly on the body 10 is not transmitted to the support member ..24 while the support member 24 is being raised yafterthe cooking stroke. This results in a downwardly directed compo-y nent of hydrostatic force which is the hydrostatic force on an area equal to that cross sectional-area Yof the support member which is not .subject to the upward force of the hydrostatic pressure of such drilling fluids.v The net downwardly directed hydrostatic force -onthe support member,24 that must be overcome y'when this support member 24 is raised is equal to the hydrostatic force Qnanarea Occupied-by the-Wall thikaessof .the least-diameter portion of the support member Z4 eX- terior of the body which portion is the torque rod 30. Therefore, the exposed area on the lower side of the balancing piston 84 in excess of the wall thickness of the connecting rod 86 is 7approximately equal to the area occupied by the wall of the torque rod 30. The upward hydrostatic force on this lower balancing piston 84 eliminates the effect of the net downwardly directed hydrostatic force that must be overcome when raising the support member 24, which is considerable in deep wells, and the upward movement of the support member 24 may be accomplished without having to overcome this hydrostatic force.

It should be noted that the length of the connecting rod 36 is such that when the support member 24 is in its uppermost position as illustrated in Figure 2 the balancing piston 84 does not contact the lower partition 22. The air or other compressible gas existing in the lower chamber 13 between the balancing piston 84 and lower partition 22 is easily compressed upon such upward movement of the balancing piston 84.

in operation, the intermediate chamber 16 is substantially filled with a noncompressible liquid through the port '81) and the upper chamber 14 below the upper piston 4S is filled with gas under high pressure through the port 76. Ordinarily, the pressure of the gas, preferably nitrogen, would be of the order of the pressures of the formation at which the tool is to be used; although, other pressures may be used. The hydraulic jar then may be threaded into a string of pipe for ordinary drilling operations or may be threaded to a string of pipe and a fishing tool for running ordinary fishing operations, as desired.

Assuming that the hydraulic jar is connected in a string of pipe during normal drilling operations, uid may be circulated downwardly through the string of pipe 34, through the tool, and downwardly to the bit and out to perform its usual function. In the event the bit and/ or part of the string of pipe to which it is connected becomes stuck or lodged in the well bore, the pipe and/or bit may be jarred loose in the following manner. All or a portion of the weight of the string of pipe above the tool is permitted to bear on the jar which lowers the support member 24 thereby moving the cooking piston 26 downwardly which engages the upper piston 48 and moves the hammer element 46 downwardly into the position illustrated in Figure l. This downward movement serves to cock the hammer element 46. When the lower piston 50 moves downwardly the noncompressible liquid in the middle chamber 16 will ilow rapidly through the check valve assembly 70 and the fluid passage 72 permitting the lower piston 50 to rapidly iit into the delay sleeve 66 thereby permitting rapid and ready cooking of the hammer element 46. This same downward movement of the support member 24 through the action of the connecting rod 86 moves the balancing piston 84 downwardly into the position shown in Figure l.

When it is desired to exert a force upon stuck pipe or tools or both, the string of pipe 34 to which the support member 24 is connected is elevated at the surface to raise the cooking piston 26 to the position illustrated in Figure 2 and an upward stress taken on the body 10. During this upward movement of the support member 24 the hydrostatic force directed upwardly below the balancing piston 84 and acting on it overcomes the net downwardly directed hydrostatic force on the support member 24 so such hydrostatic force need not be overcome by pulling upwardly on the drilling string. Due to the slowness of leakage of liquid about the lower piston 50 in the confined space of the delay sleeve 66 at the lower end of the middle chamber 16 the hammer element 46 which is forced upwardly by the pressure of the gas under the upper piston 4S is initially restrained from upward movement and considerable upward strain may be exerted on the hydraulic jar pipe and tools to which it is connected before the jarring action takes place. After a short time interval the lower piston Si? will move out of the confined space of the delay sleeve 66 thereby permitting the liquid in the middle chamber 16 to by-pass the lower piston 50 between the guide lugs 68. The tremendous pressure of gas between the under side of the upper piston 48 and the upper side of the upper partition 20 will urge the hammer element 46 violently upward. Depending upon the length of the piston rod 52 connecting the lower piston 50 and the upper piston 4S, a violent impact will occur between the upper surface of the upper piston 4S, which may be throught of as hammer surface, and the lower surface of the tcocking piston 26, which is in eifect an anvil surface. This arrangement is illustrated in Figure 3 showing the parts in position at the moment of impact.

lf desired, the piston rod 52 may be shortened so that the upper surface of the lower' piston Sti is the hammer surface and the lower surface of the upper partition 20 is the anvil surface. Obviously, if desired, both the lower surface of the cocking piston 26 and lower surface of the upper partition 20 may be impacted simultaneously.

When the cooking piston 26 is struck the force of the impact on this cooking piston 26 is transmitted to the body 10 through the contact of the cooking piston 26 with the shoulder 44 in the upper chamber 14 although, if desired, the upper ends of the keys 36 could be in contact with the upper end of the body l@ and transmit the force of this blow on the cocking piston 26 to the body 10.

Thus, a violent jarring action is provided to the string of pipe and tools secured thereto, which jarring action takes place when the string of pipe and tools are under an upward stress. The cycle of jarring may be repeated as many times as desired by merely lowering the string of pipe from the surface and then taking an upward stress thereon. In taking such upward stress the string of pipe 34 does not have to overcome the net downwardly directed hydrostatic force on the cocking member 24 because it is neutralized by the action of the balancing piston 84. Because the hydrostatic pressure acting on the balancing piston 84 as it overcomes in the support member 24 the jar is hydrostatically balanced regardless of the amount of hydrostatic pressure.

The cycle of jaring may be repeated as many times as is desired by merely lowering the string of pipe from the surface and then taking an upward stress thereon. When the tool or pipe has become dislodged, the drilling operation may be continued without the necessity of removing the tool, or string vof pipe to the surface or the pipe and hydraulic jar may be removed as desired.

It is apparent that numerous changes in details and rearrangements of the parts may be made, and the hydrostatically balanced jar is well adapted to carry out the objects set forth and other objects inherent therein.

Accordingly, it is desired to be limited only by the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. A hydrostatically balanced jar for use in a well bore comprising; a substantially tubular first member adapted for insertion in the well bore having upper and lower aligned piston chambers; an axial passageway connecting said piston chambers; an elongate support member having a longitudinal passageway throughout and having a portion extending into the upper piston chamber, said support member being slidable relative to the irst member; engageable stop means on the rst member and support member to limit upward movement of the support member relative to the rst member; an elongate hammer element slidable in the iirst member having a longitudinal passageway throughout and including a piston located in the upper piston chamber; means within the rst member for urging the hammer element violently upward; delay means associated with the hammer element retarding upward movement of the hammer element during an initial part of its upward movement; a balancing piston in th'e lower piston chamber' exposed to well iiuid pressure on its underside; a rigid tubular connecting rod secured to the support member and balancing piston and slidably extending through the passageway connecting the piston chambers and the passageway through the hammer element, said balancing piston having a uid passageway therethrough in communication with the interior of the tubular connecting rod, said balancing piston having an exposed underside of area approximately equal to the area occupied by the wall thickness of the connecting rod and the wall thickness of the least diameter portion of the support member exterior of the first member; means in the passageway connecting the piston chambers to sealingly engage the connecting rod against iiuid passage exterior of the connecting rod; said portion of the support member extending into said upper piston chamber engaging said hammer element to force the hammer element downwardly thereby cooking the jar on such downward movement of the support member relative to the lirst member; the delay means delaying for a substan tial period the occurrence of a blow by said hammer element until the support member may be elevated to engage the stop means and exert a direct upward stress on said first member.

2. A hydrostatically balanced hydraulic jar for use in a well bore comprising; a substantially tubular rst member adapted for insertion in the well bore; upper and lower partitions within the lirst member spaced from ends of the iirst member separating the lirst member into upper, middle, and lower piston chambers; mutually aligned passageways through the partitions; an elongate support member having a longitudinal passageway throughout and having a portion extending into the upper piston chamber, said support member being slidable relative to the iirst member; engageable stop means on the first member and support member to limit upward movement of the support member relative to the first member; an elongate hammer element having a longitudinal passageway throughout, said hammer element including an upper piston located in the upper piston chamber, a piston rod secured to the upper piston and slidably extending downwardly through the passageway in the upper partition, and a lower piston secured to the piston rod and located in 'the middle piston chamber, said hammer element being slidable relative to the irst member; means in the upper partition to sealingly engage the piston rod against fluid passage externally thereof; valve means to add gas under pressure within the upper piston chamber under the upper piston for urging the hammer element violently upward; delay means associated with the hammer element retarding upward movement of the hammer eler-.ient during the initial part of its upward movement; a balancing piston' inthe lower piston chamber exposed to well fluid' on its underside; a rigid tubular connecting rod secured .to the support member and balancing piston and slidably extending through the lower partition and the passageway through the hammer element, said balancing piston having a uid passageway therethrough communication with the interior of the tubular connecting rod, said balancing piston having an exposed underside of area approximately equal to an area occupied by wall thickness of the connecting rod and the wall thickness ol' the least diameter portion of the support member exterior of the irst member; means in the lower partition to sealingly engage the lower partition and connecting rod against i'luid passage external of the connecting rod; said portion of the support member extending into said upper piston chamber engaging said hammer element to force the hammer element downwardly thereby cooking the jar on downward movement of the support member relative to the first member, the delay means delaying for a substantial period the occurrence of a blow by the hammer element until the support member may be elevated to engage the stop means and exert a direct upward stress on said first member.

3. The invention of claim l in which the means within the first member for urging the hammer element violently upward includes gas under pressure.

4. The invention of claim 2 in which the delay means includes a small bore portion in the middle piston charnber spaced below the upper partition closely fitting the lower piston and a fluid by-pass around the lower piston from below the small bore portion to above the small bore portion; and valve means to add a substantiallynon-compressible liquid substantially lling the middle piston chamber.

5. The invention of claim 2 in which the means within the first member for urging the hammer element vio lently upward includes gas under pressure.

References Cited in the tile of this patent UNITED STATES PATENTS 2,626,7Sl Reynolds Jan. 27, 1953 2,801,078 Medders et al. July 30, 1957 

